Grommets for a wire harness are made of a rubber or an elastomer. A grommet includes a smaller diameter tubular section where a group of electrical wires that constitute the wire harness can pass through closely, and a larger diameter tubular section connected to an outer peripheral surface of the smaller diameter tubular section to enlarge a diameter and provided on its outer peripheral surface with an annular vehicle body latch recess. A distal end of a side wall of the vehicle body latch recess is provided with a sealing lip to be pushed onto the vehicle body. Previously, the grommet was temporarily pushed into the inside of the motor vehicle from the outside via a through-hole and then the grommet was pulled outward so that the vehicle body latch recess is engaged with an edge around the through-hole, thereby preventing the sealing lip from being bitten.
However, a relatively great inserting force is required to insert the larger diameter tubular section of the grommet into the through-hole. This lowers workability and productivity.
In order to overcome the above problem, the present applicant proposed a grommet with a larger diameter tubular section that is extendable, as shown in FIGS. 9A to 9E, in JP 2009-201204 A. In JP 2009-201204A, a grommet 100 includes a smaller diameter tubular section 101, a larger diameter tubular section 102, and a U-shaped turning portion 103 between the sections 101 and 102. As shown in FIGS. 9B to 9D, when pushing the grommet 100 into a through-hole H in a vehicle body panel P, a wire harness 110 is pushed inward to extend the turning portion 103 in a straight state, thereby decreasing an inserting force. After a vehicle body latch recess 105 is engaged with an edge around the through-hole H, the wire harness 110 is pulled in a reverse direction to return the turning portion 103 to the original U-shape, as shown in FIG. 9E.
In the grommet having the extendable function disclosed in JP 2009-201204A, extending and deforming the turning portion 103 from a position shown in FIG. 9A to a position shown in FIG. 9B to extend the larger diameter tubular section is carried out so as to extend the entire turning portion 103 in one stroke before inserting the grommet 100 into the through-hole H in the vehicle body panel P. However, it is preferable that the turning portion 103 can extend automatically in response to the inserting work into the through-hole H, without extending the turning portion 103 beforehand. There is also a problem that the turning portion 103 is hard and difficult to extend at the starting time of extension. In particular, there is a problem that extension of the turning portion is difficult if an amount of extension is small.
Recently, in hybrid motor vehicles or electric motor vehicles, there are instances where a smaller diameter tubular section of a grommet is mounted on a pipe harness in which a wire harness to be arranged under a floor of the motor vehicle is inserted into a metal pipe, and the grommet is attached to a through-hole in a floor panel. The smaller diameter tubular section of the grommet is likely to adhere to an outer peripheral surface of the pipe of the pipe harness to be easily displaced in connection with displacement of the pipe. Consequently, the smaller diameter tubular section is likely to pass over a given position before the vehicle body latch recess of the larger diameter tubular section of the grommet is engaged with the through-hole. Accordingly, if the smaller diameter tubular section becomes readily extendable in response to displacement of the pipe, it is possible to enhance workability in insertion of the grommet.